1. Field of the Invention.
The present invention relates to solid phase extraction generally and, more particularly, but not by way of limitation, to a novel eluter for a solid phase extraction system method that simultaneously aspirates multiple samples to be processed by solid phase extraction through a unique defined area for each sample in the defined area to contain various solid phase extraction elements, without an intervening liquid transfer step, and eluting the samples to an analyzer.
2. Background Art.
High performance liquid chromatography (HPLC) and mass spectrography (MS) are commonly used for the analysis of various chemical products. HPLC and MS have the unique ability to identify specific chemical entities within a mixture of components. A very common use is in drug research and development in the pharmaceutical industry.
In many cases, it is mandatory that the sample be preprocessed or xe2x80x9ccleaned upxe2x80x9d using solid phase extraction (SPE), prior to HPLC or MS. This is normally done by passing the sample through a silica bed. There are different silicas depending on the desired end product. C18 is a common SPE grade of silica and there are others. The component of interest, normally a chemical compound (e.g., a drug) is present mixed with other components within the sample. To analyze the compound of interest, it must first have some form of separation from the rest of the sample. Otherwise, the signal-to-noise ratio would be such that the component of interest could not be detected with sufficient precision.
SPE is the typical technique that is employed. The unique aspect of this technique is that the retention of the compound is a function of the solvent flowing through the silica. Thus, an aqueous solution flowing through the silica will cause certain compounds to be retained. If an organic solvent is then passed through the silica, the retained compound can be released or eluted into the solvent. This is SPExe2x80x94the use of silica to separate compounds of interest from other materials.
In the late 1980xe2x80x2s, cartridges of silica came on to the market. A common format used was the barrel of a 10 mL disposable syringe. In the middle to late 1990xe2x80x2s, the need for higher throughput moved solid phase extraction to the 96-well format of microplates. The 10 mL syringe barrels were replaced by the columns in a deepwell microplate. This facilitated processing the samples through the silica columns with a 96-well pipettor.
Recently, 3M Company introduced its Empore(copyright) product in the 96-well format. This consists of silica supported in a Teflon(copyright) matrix. One advantage of this construction is that it provides for very small volume retention This is of critical importance as the total volume of the sample becomes smaller. Empore(copyright) elements are located in the bottoms of the SPE columns. Other techniques use more silica within the column. The end result serves the same purpose.
The incoming samples normally arrive in a 96-well format, although other formats can be employed as well Using individual or multi-well pipettors, the 96 samples are transferred to the 96 SPE columns Vacuum is used to move the samples through the silica. The compounds of interest are then retained on the silica, with the balance of the streams going to waste.
The next step is to place a capture plate under the SPE columns. Then, solvent of choice is added to the columns using the pipettor Vacuum is again used to create flow through the SPE columns This time, however, the eluent is captured in individual wells under each respective SPE column These 96 extracted samples are then transported to a sampling device that injects each sample individually into an analyzer. This normally is an HPLC instrument or an MS instrument or a combination of HPLC and MS instruments.
It will be appreciated that the above conventional techniques require a three-step process that involves three different types of equipment as well as involving multiple handling of the sample materials
Accordingly, it is a principal object of the present invention to provide an eluter for a simplified SPE system that reduces the different types of equipment required.
It is a further object of the invention to provide such eluter that reduces the handling of sample materials.
Another object of the invention is to provide such eluter that is simple and economical.
Other objects of the present invention, as well as particular features, elements, and advantages thereof, will elucidated in, or be apparent from, the following description and the accompanying drawing figures.
The present invention achieves the above objects, among others by providing, in a preferred embodiment, an eluter instrument for an SPE system, comprising a housing, an upper seal mounted in said housing for up and down motion with respect thereto, a lower seal mounted in said housing for up and down motion with respect thereto, and said upper seal and said lower seal being moveable between a first position in which said upper seal and said lower seal are spaced apart and not in proximity and a second position in which said upper seal and said lower seal are in proximity and spaced apart sufficiently only to clamp therebetween a first area of a plurality of areas of an SPE medium, said first area containing therein one or more compounds of interest, such as to permit elution of said one or more compounds of interest to another instrument.